MadeEasy Test Series: Computer Networks - Network Protocols

Question

Which of the following option is false?

 

A An ARP request packet include MAC address field and IP addresses of the receiver contains all 0’s

B BOOTP messages are encapsulated in a UDP packet.

C ICMP reports error message to the original source.

D ICMP messages can’t be used to determine the round-trip time needed for an IP datagram to travel between them.

Comments

Option A must be false

Because 0.0.0.0 is used when anyone doesn't know its own IP, basically used in RARP. to get own IP from Router.

in ARP exact IP must be present and packet is broadcasted.

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Given answer is d

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@Ashwin Kulkarni 

i think option (A) is true because ARP Request is a broadcasting request. and here if the destination would be in different network then instead of asking for mac address of some specific destination, It will ask mac id to the router and therefor packet may contain ip to be 0.0.0.0 also. 

Answer 1

Answer (D)

Option A) True

ARP Request is a broadcasting request. and here if the destination would be in different network then instead of asking for mac address of some specific destination, It will ask mac id to the router and therefor packet may contain ip to be 0.0.0.0 also. 

Option B) True

BOOTP is doing nothing more than request and reply and it does not need any resource reservation thus it mostly encapsulated in a UDP packet always.

Option C) True

Option D) False

ICMP is able to do timestamp request and reply. it contain a field called timestamp and the originate timestamp is the time the sender last touched the message before sending it, the receive Timestamp is the time the echoer first touched it on receipt, and the transmit Timestamp is the time the echoer last touched the message on sending it.

http://www.networksorcery.com/enp/protocol/icmp/msg13.htm

Comments

How can option A is true .When host want to send packet to reciever in another network..we should send packet to default router of network...and IP address of default router need not be 0.0.0.0

correct me if i am wrong ..

Answer 2

D is False:

The round trip time is not actually stored anywhere. The sending host remembers the time it sends each ICMP Echo Request message, using ICMP's 16-bit identifier and sequence fields. When it gets the ICMP Echo Reply, it notes the current time, finds the time it sent the matching Request packet identified by the reply, calculates the difference, and reports it as RTT

https://networkengineering.stackexchange.com/questions/53253/where-is-pings-round-trip-time-stored-in-the-ip-header

A is False 

How does ARP resolve an IP address to an Ethernet MAC address?
When ARP needs to resolve a given IP address to Ethernet address, it broadcasts an ARP request packet. The ARP request packet contains the source MAC address and the source IP address and the destination IP address. Each host in the local network receives this packet. The host with the specified destination IP address, sends an ARP reply packet to the originating host with its IP address.

https://www.netometer.com/qa/arp.html#:~:text=The%20ARP%20request%20packet%20contains,host%20with%20its%20IP%20address

B and C are trivial options